1. Field of the Invention
The present invention relates to a machine for exchanging old ties of a railroad track for new ties, the track being comprised of two rails fastened to the ties defining cribs therebetween and the rail having gage and field sides, which comprises a machine frame supported by undercarriages for mobility along the track, a longitudinally, vertically and transversely displaceable tie exchange device connected to the machine frame for laterally pulling the old ties out of the track and laterally inserting the new ties in the track at a tie exchange position, and a ballast scarifying device for clearing ballast at the tie exchange position.
Throughout the specification and claims, the directional terms "transversely" and "longitudinally" refer to the direction with respect to the longitudinal extension of the track.
2. Description of the Prior Art
European patent No. 0 057 128, published Aug. 4, 1982, discloses a tie exchanging machine of this general type, which comprises a tie exchange device for pulling the old ties and inserting the new ties, and a ballast scarifying device equipped with a ballast excavator for clearing the ballast at the tie exchange site, which is suspended on the machine frame by a parallelogram guide for longitudinally displacing the ballast scarifying device. The lower end of this complex mechanism is supported on the track by small retractible wheels. With this ballast scarifying device, the ballast is skimmed and temporarily stored in the excavator after the old tie has been pulled out and before the new tie is inserted at the tie exchange site. While the new tie is inserted, the ballast scarifying device is longitudinally displaced from the tie exchange site and, after the new tie has been inserted, the stored ballast is emptied thereover from the excavator. The longitudinally displaceable ballast scarifying device is relatively complicated because it requires not only power-actuated drives for the operating displacement of the excavator but additional power-actuated drives for the displacement of the lower portion of the device supported by the wheels on the track relative to the upper portion suspended from the machine frame.
U.S. Pat. No. 4,955,301, dated Sep. 11, 1990, discloses a tie exchange train comprising a series of bridge-like machine frames coupled to each other and carrying different tie exchange devices longitudinally displaceably mounted on the machine frames. The old ties are removed by a tie exchange device mounted on a bridge-like machine frame at the front of the train and the new ties are inserted by a tie exchange device mounted on a bridge-like machine frame at the rear of the train. The tie exchange devices are arranged on a longitudinally extending auxiliary carrier which is longitudinally displaceable and has one end supported on the railroad track by an undercarriage while an opposite auxiliary carrier end is pivotally supported on the machine frame. The old ties are deposited from the tie exchange device withdrawing the old ties from the track on a conveyor band extending below the auxiliary frame. The conveyor band conveys the old ties from an end of the conveyor band adjacent the tie exchange device to an opposite conveyor band end where they are transferred to an ascending conveyor. The old ties collected on the ascending conveyor are conveyed to a storage area on top of the machine frame where the old ties are stacked. The stack of old ties is then removed by means of a mobile crane which is mounted on, and runs along, the train. The new ties are similarly, and in reverse order, conveyed to the tie exchange device which inserts the new ties in the track. This machine includes a further bridge-like machine frame under which a ballast scarifying device is mounted on an independently movable carriage whose ends are supported by undercarriages on the track. The ballast scarifying device has vertically and transversely adjustable ballast clearing and planing elements. Such a tie exchange train works very efficiently for exchanging ties, particularly in groups of three or four adjacent ties, in an assembly line fashion as the train advances continuously along the track.